In a printing system using a digital copying machine, a method of allowing a printing apparatus via a network to receive and print print data generated on a network-connected client computer is available. In a POD (Print On Demand) market such as a near-print market, there is a system called a web submission system which utilizes the Internet. In this system, a predetermined procedure is executed on a homepage for web submission of a printing company and print data to be ordered to print is transmitted.
As an alternative method, there is a system which executes printing from print data stored in a removable medium in a CD-ROM drive, MO drive, or the like, connected to a printing apparatus. In this system, for example, when a user brings print data directly to a printshop, he or she stores the print data generated on a client computer in an external storage device such as a removable medium connected to the computer. The print data stored in the removable medium or the like is submission data in a form of PDL (Page Description Language) data or in a direct printable format (a format of PDF, TIFF, JPEG, or the like). The printshop executes the printing directly from the removable medium or the like.
The above printing method is not only aimed at printing at a printshop or the like but is also applied to printing for personal use using a printing apparatus away from home. That is, when a printing apparatus which a user can use away from home is not connected to a network, he or she can print out print data by the printing apparatus by storing print data in a removable medium and carrying it. As a patent reference concerning the present application, Japanese Patent Laid-Open No. 2004-042394 (patent document 1) can be enumerated.
However, print data input from, e.g., a removable medium to a printing apparatus and developed to printable image data often contains classified information such as personal information. For example, in variable data printing (VDP) which switches only some part of a job to data specific to each distribution destination user and prints out the resultant data, the classified information such as user's address, birthday, and the like, is often used as a data part specific to each user.
In a printing system using a digital copying machine, developed image data and the like are generally stored in a hard disk (HDD) or the like in the printing apparatus after the data is printed out. However, in a printing system which does not have a function to completely delete the printed data, the security of the print data is not ensured perfectly since the data may be printed out by the third party without permission.
In addition, even in a printing system in which data is completely deleted after the printing process so as to improve security, labor is required to write random data many times in order to delete the data completely from the HDD. This causes adverse effect on process performance of the system.